1. Field of the Invention
The present invention relates to a system for generating hydraulic pressure, and more particularly to a hydraulic pump using shape memory alloys.
2. Description of the Prior Art
FIG. 1 illustrates a conventional hydraulic generating system 10 installed in vehicles for driving an actuator of various hydraulic systems. As illustrated, the conventional hydraulic generating system includes a pump 16 for generating hydraulic pressure and a motor 12 for driving pump 16 via a coupling 14 by means of an electric power.
Motor 12 is fixed to a base plate 18 by using bolts and the like, and pump 16 is fixed to base plate 18 while being attached to a bracket 15. Motor 12 is coupled with pump 16 by means of coupling 14.
Once electric power is supplied to motor 12, motor 12 is rotated and pump 16 which is joined to coupling 14 receives the rotational force of motor 12 via coupling 14 to generate the hydraulic pressure which, in turn, is transmitted to various hydraulic systems to drive them.
In the above conventional hydraulic generating system, however, motor 12 is required as a driving power for generating the hydraulic pressure, and coupling 15 for transmitting the power of motor 12 is a requisite element.
Furthermore, bracket 15 for attaching pump 16 thereto and base plate 18 for fixing motor 12 and bracket 15 are added, which complicates the structure, makes the weight heavy, requires high cost and is difficult to repair.
On the other hand, shape memory alloys refer alloys that preserve a shape deformed by an external force below a critical temperature, whereas a shape memory effect of the alloy is activated for recovering a memorized original shape by a shape recovering force after being heated to the critical temperature. The shape memory alloys such as a titan-nickel alloy and an aluminum alloy are fabricated at a high temperature to have a predetermined shape.
There are two methods of applying heat the shape emory alloys. In the first method, fluid is forced to flow around the shape memory alloys to change the temperature of the fluid. In the second method an electric current is forced to flow along the shape memory alloys to generate heat by an electric resistance of the shape memory alloys, thereby heating the shape memory alloys.
The shape memory alloys shaped as a spring mainly respond to the temperature of the fluid flowing around the shape memory alloys or of an object contacting the alloys. In more detail, when the temperature of the fluid flowing around the spring formed of the shape memory alloy reaches the critical temperature, the shape memory alloy spring restores its original shape; otherwise, when the temperature of the fluid goes below the critical temperature, the shape thereof is deformed by the external force.
However, a structure using the above-described shape memory alloy spring has a slow response rate with respect to the temperature of the fluid, and it is difficult to accurately control the operative range of the shape memory alloy spring. Furthermore, the shape of the shape memory alloy spring is complicated, thereby making manufacturing difficult.